1. Field of the Invention
The present invention relates to a sheet processing device that applies specific processing on a sheet and to an image forming apparatus that adopts the sheet processing device as a post-processing device.
2. Description of the Related Art
Post-processing devices as disclosed in JP-A-2003-128293 and JP-A-2005-154034 have been known. These post-processing devices each apply specific post-processing (alignment processing and staple processing) on sheets successively fed therein from the image forming apparatus. These post-processing devices each include a processing tray provided diagonally, an endless belt provided to sandwich the main surface side and the back surface side of the processing tray and having a pair of claw members to move up and down sheets, a stapler that applies staple processing on a pile of sheets stacked on the processing tray and supported on the claw member, and so forth.
A pile of sheets is formed as a specific number of sheets are discharged successively onto the processing tray from the image forming apparatus and received by one of the claw members. This pile of sheets is moved to the position of the stapler by the circulation of the endless belt and the staple processing is applied to the pile of sheets at the moved position. The pile of sheets after the completion of the staple processing is moved up along the processing tray with the movement of the claw member by the circulation of the belt and discharged to the outside. One of the claw members after the pile of sheets is discharged comes around toward the back surface of the processing tray with the circulation of the endless belt. Meanwhile, the other claw member moves toward the main surface and stands by for the feeding of a sheet for the next job onto the processing tray.
JP-A-2005-154034 supra describes that the claw members are allowed to function as alignment means (line-up means) for a pile of sheets in the transportation direction thereof. This patent document, however, merely discloses that two claw members functioning as the alignment means are simply provided to the endless belt, and improvement in efficiency of the alignment processing on a pile of sheets, avoidance of interference with a pile of sheets to be discharged onto the processing tray, and so forth are not fully taken into account.